Metallurgical Examination of a Galled PH 13-8 Mo Stainless Steel Main Rotor Sub-Assembly

摘要

The Aviation and Missile Command (AMCOM) requested the US Army Research Laboratory (ARL) to perform a metallurgical examination of a Main Rotor Sub-assembly from an attack helicopter. During a test flight after replacement of the main rotor head, the pilot noticed a vibration. Post flight inspection revealed both the upper and back lead-lag link bearings displaced on one of the four main rotor strap packs. Further inspection and disassembly revealed broken components that secured a rotor blade on the outboard end of a strap pack (connection assembly).